Audio processing device and method of providing information

ABSTRACT

An audio processing device has an information extractor that extracts identification information from a first audio signal in a first frequency band that includes an audio component of a sound for reproduction and an audio component including the identification information of the sound for reproduction and a signal processor that generates a second audio signal that includes the identification information extracted by the information extractor and that is in a second frequency band higher than the first frequency band, with a sound represented by the second audio signal being emitted from a sound emission device.

TECHNICAL FIELD

The present invention relates to a technique for processing audio signals.

BACKGROUND ART

Services that provide users with guidance information on public transportation services in the form of automated sounds are in wide use. For example, announcement systems used in buses provide passengers with guidance information by way of voice guidance on, for example, bus stops, bus fares, and the like, which guidance voice is played at an appropriate timing, for example at each of bus stops, upon operation of an operator, with such voice guidance being pre-prepared for each of bus routes. Patent Document 1 discloses a configuration in which information such as names of bus stops is announced to passengers through the generation of voice signals that correspond to voice data based on operations such as an input operation into a device installed in a bus carriage. Patent Document 2 discloses a configuration for the creation of voice data corresponding to a guidance voice whereby, supposing that a content of voice guidance is a sentence such as “the next stop is [name of a bus stop]”, names of bus stops are created by utilizing low-compression coding, while common words such as “next”, “is”, and the like are created by utilizing high-compression coding.

RELATED ART DOCUMENT(S) Patent Document(S)

Patent Document 1: Japanese Utility Model Registration Application Laid-Open Publication No. S61-116400

Patent Document 2: Japanese Patent Application Laid-Open Publication No. H08-008855

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

A technique by which information is distributed to terminal devices using transmission of sound waves (hereinafter, “audio communication”) is practiced in the art. In audio communication, information is distributed to and received by terminal devices upon emission of a sound that represents an audio signal in which information for distribution is contained within a high and inaudible frequency range, for example, from 18 kHz to 20 kHz. In this example, application of audio communication to the voice guidance systems exemplified in Patent Documents 1 and 2 is assumed. It is common for external environment noise, such as engine noise, and vibration noise to intrude into the interior of a bus. To enable passengers to clearly comprehend voice guidance, audio components in a lower frequency audible range of the audio signal, for example, of equal to or less than approximately 16 kHz, may be filtered in, while those in the higher range may be omitted. For this reason, upon application of audio communication as disclosed in Patent Documents 1 and 2, distribution information contained in a high frequency band is prevented from being output (emitted). While the explanation above relates to buses used for public transportation, the same problem is liable to occur in any environment in which a variety of information is provided to users, such as other public transportation services, or within public facilities, and others. In view of the above-described matters, an object of the present invention is to provide appropriate audio communication in an environment in which certain frequency bands are suppressed.

Means of Solving the Problems

To solve the abovementioned problems, an audio processing device according to a first aspect of the present invention includes: information extraction means that extracts identification information from a first audio signal in a first frequency band in which audio signal there are included an audio component of a sound for reproduction and an audio component including the piece of identification information of the sound for reproduction; and second audio signal generation means that generates a second audio signal that includes the identification information extracted by the information extraction means, and is in a second frequency band, which frequency band is higher than the first frequency band, and wherein a sound represented by the second audio signal is emitted by sound emission means. According to the above configuration, an audio component of the sound for reproduction, for example, guidance voice for provision to a user, and an audio component including the identification information of the sound for reproduction are each included in the first audio signal in the first frequency band, while the identification information extracted from the first audio signal is included in the second audio signal in the second frequency band. According to the above embodiment, it is possible to collectively and appropriately transmit (broadcast) identification information to proximate devices via audio communication by utilizing the second frequency band, even in an environment in which the second frequency band is suppressed in the first audio signal. The second frequency band is, for example, in a high range of between 16 kHz and 20 kHz, and more preferably, within a range of between 18 kHz and 20 kHz. Examples of a “sound for reproduction” include sound of guidance information for provision to users of a public facility or a public transportation service, as in, for example, respectively, facility information on opening and closing hours, or information on transfer locations, fares, and so forth.

In a preferred embodiment of the present invention, the audio processing device includes: sound receiving means that receives a sound represented by a reproduction signal in which there are included the audio component of the sound for reproduction and the audio component that includes the identification information of the sound for reproduction, for generation of the first audio signal; and sound emission means that emits a sound represented by the second audio signal generated by the second audio signal generation means. According to this embodiment, it is possible to appropriately transmit the identification information via audio communication without need to change an existing system that emits a sound indicated by the reproduction signal in which the second frequency band is suppressed. Emission of the sound represented by the second audio signal includes emitting a sound represented by a signal obtained by synthesizing with the second audio signal another different signal, for example, an audio component of the reproduction signal.

In another preferred embodiment of the present invention, a length of time over which the sound represented by the second audio signal is emitted by the sound emission means is longer than a length of time over which the audio component including the identification information of the sound for reproduction within the reproduction signal is emitted. In this way, it is possible to ensure that sufficient opportunity exists for the terminal device at the receiving side to receive the identification information contained in the second audio signal. The first frequency band, for example, is set to be within an audible range, while the second frequency band is set to be within a range higher than the first frequency band, namely, a frequency band that is barely audible to a user. However, in this case, the user may perceive incongruity or discomfort if the audio component in which the identification information is contained is emitted for a protracted length of time. According to the above embodiment, however, a length of time over which the sound represented by the second audio signal in the second frequency band is emitted is set to be longer than a length of time over which the audio component including the identification information within the reproduction signal of the first frequency band is emitted. In short, the identification information emitted via audio communication in which the sound in the second frequency band is utilized and which is barely audible to the user is transmitted for comparatively longer period of time. In this way, it is possible to reduce a likelihood of the user perceiving incongruity or discomfort that may otherwise result from the audio component in the first frequency band that includes the identification information of the sound for reproduction being transmitted for a protracted period of time. It is also possible to notify each terminal device of the identification information without causing the user to perceive incongruity or discomfort, and to allow each terminal device to re-acquire the identification information in the event that initial receipt of the identification information is not successful.

Preferably, a period in which the sound represented by the second audio signal is emitted by the sound emission means and a period in which the audio component of the sound for reproduction within the reproduction signal is emitted may overlap. According to this embodiment, since the audio component including the identification information is emitted in parallel to the emission of the corresponding sound for reproduction, it is possible for the terminal device of the user to acquire, closer to real-time, information corresponding to the notified identification information, as compared, for example, to a configuration in which the identification information is notified after playback of the sound for reproduction is complete.

In yet another preferred embodiment of the present invention, a reproduction signal is supplied, as the first audio signal, from a reproduction processing device to the information extraction means via a signal line, the reproduction processing device generating the reproduction signal that includes the audio component of the sound for reproduction and the audio component that includes the identification information of the sound for reproduction. According to this embodiment, since the audio processing device generates the second audio signal that includes the identification information extracted from the first audio signal in which the second frequency band is suppressed, it is possible to appropriately transmit the identification information without any need to change the existing system. Furthermore, because the reproduction signal is supplied as an audio signal to the information extraction means via the signal line, it is not necessary to install a sound receiving device in the audio processing device. Accordingly, an advantage is realized in that configuration of devices can be simplified, in contrast to a set-up in which a sound receiving device is provided.

The audio processing device according to a second aspect of the present invention includes: information extraction means that extracts identification information from a first audio signal that includes an audio component of a sound for reproduction and an audio component that includes the identification information of the sound for reproduction; transmission signal generation means that generates a transmission signal that includes the identification information extracted by the information extraction means; and transmission means that transmits an electromagnetic wave indicative of the transmission signal generated by the transmission signal generation means. Examples of communication using electromagnetic waves include Wi-Fi (registered trademark), Bluetooth (registered trademark), and infrared communication. According to the above embodiment, it is possible to distribute information by use of a variety of different transmission media, and thus it is possible to appropriately transmit the identification information even in an environment in which a particular frequency band is suppressed.

The audio processing device according to the second aspect may include sound receiving means that receives a sound represented by a reproduction signal that includes the audio component of the sound for reproduction and the audio component that includes the identification information of the sound for reproduction, for generation of the first audio signal. Alternatively, the reproduction signal may be supplied as the first audio signal from a reproduction processing device that generates the reproduction signal to the information extraction means via a signal line. According to the abovementioned embodiments, since the audio processing device generates a transmission signal that includes the identification information extracted from the first audio signal in which the second frequency band is suppressed, it is possible to appropriately transmit the identification information by way of electromagnetic waves without any need to change the existing system. Furthermore, in the configuration in which the first audio signal is supplied to the information extraction method via a signal line, it is not necessary to install a sound receiving device in the audio processing device, and thus it is possible to simplify the configuration of the devices as compared to a set-up in which a sound receiving device is installed.

With respect to the audio processing device according to the first or second aspect, the sound receiving means preferably is provided close to the sound emission device that emits the sound represented by the reproduction signal. According to this configuration, since the sound receiving device is provided close to the sound emission device that emits the sound represented by the reproduction signal, interference caused by noise can be avoided.

The present invention may also be characterized as a program that causes a computer to execute the different functional elements that the audio processing device according to each of the abovementioned embodiments includes, and a computer-readable recording medium in which the program is installed. In other words, a first aspect of the program of the present invention causes a computer to execute information extraction processing for extracting identification information from a first audio signal in a first frequency band in which audio signal there are included an audio component of a sound for reproduction and an audio component that includes the identification information of the sound for reproduction; and a second audio signal generation processing for generating a second audio signal that includes the identification information extracted in the information extraction processing, and is in a second frequency band, which frequency band is higher than the first frequency band, wherein a sound represented by the second audio signal is emitted by sound emission means. A second aspect of the program of the present invention causes a computer to execute information extraction processing for extracting identification information from a first audio signal that includes an audio component of a sound for reproduction and an audio component that includes the identification information of the sound for reproduction; transmission signal generation processing for generating a transmission signal that includes the identification information extracted in the information extraction processing; and transmission processing for transmitting an electromagnetic wave indicative of the transmission signal generated in the transmission signal generation processing.

Furthermore, the present invention may also be identified as an information providing method in which there is utilized the audio processing device according to each of the abovementioned embodiments. In other words, an information providing method according to the first aspect of the present invention extracts identification information from a first audio signal in a first frequency band in which audio signal there are included an audio component of a sound for reproduction and an audio component that includes the identification information of the sound for reproduction; generates a second audio signal that is a signal including the identification information and that is in a second frequency band, which frequency band is higher than the first frequency band; and emits a sound represented by the second audio signal. The information providing method according to the second aspect of the present invention extracts identification information from a first audio signal that includes the audio component of a sound for reproduction and the audio component that includes the identification information of the sound for reproduction; generates a transmission signal that includes the identification information; and transmits an electromagnetic wave indicative of the transmission signal.

The information providing method, the program, and the computer-readable recording medium with the program installed therein, each of which may be realized according to one or other of the above preferred embodiments, realizes substantially the same effects as those realized by an information management system according to the abovementioned embodiments.

The information providing method according to the first aspect of the present invention emits the audio component of the sound for reproduction after the emission of the audio component that includes the identification information of the sound for reproduction, and a period in which the sound represented by the second audio signal is emitted and a period in which the audio component of the sound for reproduction overlap. According to this embodiment, it is possible to transmit the identification information by audio communication, for example, in parallel to the playback of the sound for reproduction, since the audio component of the sound for reproduction is emitted after the emission of the audio component that includes the identification information of the sound for reproduction is complete.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a voice guidance system 1 of a first embodiment.

FIG. 2 is a block diagram showing a reproduction system 100 of the first embodiment.

FIG. 3 is a block diagram showing a signal synthesizer 104 of the first embodiment.

FIG. 4 is a characteristic diagram illustrative of a filter 108 of the first embodiment.

FIG. 5 is a diagram illustrative of a time length of a modulation signal A_(D), a target signal A_(G) and a second audio signal S₂.

FIG. 6 is a flowchart showing a flow of an operation carried out in the reproduction system 100.

FIG. 7 is a block diagram showing an audio processing device 200 of the first embodiment.

FIG. 8 is a flowchart showing a flow of an operation carried out in the audio processing device 200.

FIG. 9 is a block diagram showing a terminal device 300 of the first embodiment.

FIG. 10 is a diagram illustrative of a data structure of a guidance information table TB₁.

FIG. 11 is a diagram illustrating a display example of guidance information presented in a presenter 308.

FIG. 12 is a block diagram showing the reproduction system 100 of a second embodiment.

FIG. 13 is a block diagram showing a reproduction system 100 and an audio processing device 200 according to a modification of the second embodiment.

FIG. 14 is a block diagram showing an audio processing device 200 of a third embodiment.

FIG. 15 is a block diagram showing a reproduction system 100 according to another modification.

MODES FOR CARRYING OUT THE INVENTION First Embodiment

Description will now be given of an overview of a voice guidance system 1 of the first embodiment. In the following, an example configuration is described in which the voice guidance system 1 of the first embodiment is used for onboard audio announcements for a public transportation service. The voice guidance system 1 provides passengers of a public bus with voice guidance by way of guidance voice (sound for reproduction) that represent guidance information, for example, guidance on bus stops, fares, or on tourist sites, or a surrounding area, and so forth.

FIG. 1 is a diagram showing a configuration of the voice guidance system 1 of the first embodiment. The voice guidance system 1 includes a reproduction system 100, an audio processing device 200, and a terminal device 300. The reproduction system 100 and the audio processing device 200 are installed inside a carriage C of a public bus service.

The reproduction system 100 emits inside the carriage C, along with a guidance voice, a sound in a frequency band B₁ that includes identification information that corresponds to one of a multiplicity of guidance voices, each of which are different. A passenger of the carriage C (hereinafter, the user) hears the guidance voice. In the meantime, the audio processing device 200 extracts the identification information from the sound that the reproduction system 100 emits, so as to emit a sound in a frequency band B₂ that includes the identification information. The frequency band B₁ and the frequency B₂ are different from each other. In other words, the audio processing device 200 is a signal processing device that converts a frequency band of an audio that includes identification information to another frequency band that includes the same identification information.

The terminal device 300 is a portable communication terminal that a user in the carriage C carries with him/her (e.g., a mobile phone/smartphone), and the terminal device 300 extracts identification information of a guidance voice from a sound emitted by the audio processing device 200 and receives, via a communication network 400, for example, a mobile communication network or the Internet, from a guidance information server 500 guidance information that corresponds to the identification information. Guidance information relates to guidance provided by guidance voice. For example, any of the following may be provided to the terminal device 300 as guidance information, for reproduction, to be emitted, or displayed: characters and/or still or moving images indicative of information on user guides, such as facilities, fares, and so forth; travel guide, such as stops, transfer locations, and so forth; and tourist information for local areas close to the guided location, such as tourist facilities, accommodation, area guides such as for historic sites, and so forth; characters that represent guidance voice, for example, characters to which a hearing-impaired person may refer so as to visually check guidance information; and/or sounds and/or characters obtained by translating the guidance information provided through the guidance voice into a foreign language. Details of the different elements of the voice guidance system 1 will now be described below.

Reproduction System 100

As shown in FIG. 1, the reproduction system 100 includes an operator 110, a reproduction processing device 120, and a sound emission device 130. The operator 110 is an input device that receives instructions from the driver O_(P) of a public transportation bus. Each time the carriage C approaches a given stop, the driver O_(P) initiates playback of a guidance voice relating to the stop by operating the operator 110. The reproduction processing device 120 generates an audio signal (hereinafter, the “reproduction signal”) A₂ that represents a sound obtained by synthesizing the guidance voice that the driver O_(P) has initiated the playback of by operating the operator 110, from among multiple different guidance voices, and a sound that includes identification information of the guidance voice. The sound emission device 130 (e.g., speakers) emits a sound that represents the reproduction signal A₂ generated by the reproduction processing device 120. In FIG. 1, a single sound emission device 130 is shown, but in reality, multiple sound emission devices 130 are installed in the carriage C, and the reproduction signals A₂ are supplied in parallel thereto from the reproduction processing device 120.

FIG. 2 is a block diagram showing a configuration of the reproduction system 100. The reproduction processing device 120 of the first embodiment includes a controller 102, a signal synthesizer 104, a storage device 106, and a filter 108, as FIG. 2 shows. The storage device 106 consists of a publically known recording medium, such as, for example, a semiconductor recording medium or a magnetic recording medium, and stores, for every location (stop) at which the carriage C stops, an audio signal (hereinafter referred to as a “target signal”) A_(G) (A_(G1), A_(G2), . . . ) that indicates a guidance voice related to one such location, as well as identification information D (D₁, D₂, . . . ) of guidance information that relates to the location. The target signal A_(G) and the identification information D are not necessarily stored in the storage device 106 of the reproduction processing device 120. For example, the reproduction processing device 120 may instead receive the target signal A_(G) and the identification information D from an external device (a server device) by communicating with the external device.

Stops include not only stops that exist along the route of a public bus but also places that serve as transfer locations (for example, public transportation stations, airports, or any given location on a public roadway). The identification information D is a unique code that is used to identify the guidance information, and it is set for each location at which the bus carriage C stops (bus stop). For example, a sequence of random numbers generated by a publically known method is set as the identification information D for all guidance information so that identification information D does not overlap.

The controller 102 of FIG. 2, in accordance with the playback instruction that the operator 110 has accepted from the driver O_(P) as the carriage C approaches a stop, reads from the storage device 106 the target signal A_(G) and the identification information D that correspond to the stop and supplies the signal synthesizer 104 with the target signal A_(G) and the identification information D. The signal synthesizer 104 generates a reproduction signal A1 by synthesizing the identification information D with the target signal A_(G). Any publically known method may be used for synthesizing the identification information D with the target signal A_(G), but one preferable method is that disclosed in WO 2010/016589.

FIG. 3 is a block diagram showing a configuration of the signal synthesizer 104. As shown in FIG. 3, the signal synthesizer 104 includes a modulation processor 1042 and a synthesis processor 1044. The modulation processor 1042 generates an audio signal (hereinafter, the “modulation signal”) A_(D) that includes identification information D as an audio component in a particular frequency band by sequentially carrying out spread modulation of the identification information D using a spread code, and frequency conversion using a carrier wave in a predetermined frequency. The modulation processor 1042 synthesizes a notification sound with the modulation signal A_(D). The notification sound included in the modulation signal A_(D) is a natural sound that attracts the attention of passengers in the carriage C (e.g., a sound for guidance, such as “dingdong”). The frequency band of the modulation signal A_(D) is one in which the emission of a sound by the sound emission device 130 and the reception of a sound by the audio processing device 200 are possible, and the frequency band is included within the frequency band range of sounds of voices or music that a user is exposed to in an ordinary environment, for example, equal to or less than approximately 16 kHz, which is within an audible range. The synthesis processor 1044 generates a reproduction signal A₁ by synthesizing (typically by adding) the target signal A_(G) supplied from the controller 102 and the modulation signal A_(D) generated by the modulation processor 1042. The method by which the modulation processor 1042 generates the modulation signal A_(D) is not limited to the above example (spread modulation). For example, as an alternative, it is possible to generate the modulation signal A_(D) within a particular frequency band by frequency-modulating a carrier wave, such as a sine wave in a predetermined frequency, based on the identification information D.

The filter 108 of FIG. 2 is a low-path filter (LPF) that generates a reproduction signal A₂ by suppressing the frequency components in the higher end of the reproduction signal A₁. FIG. 4 is a characteristic diagram of the filter 108 of the first embodiment. In order for the guidance voice to be clearly perceived by passengers in the carriage C, which is subject to intrusion of exterior noise such as engine and vibration noise, the filter 108, as shown in FIG. 4, suppresses the components in the higher-end frequency band, for example, between 18 kHz and 20 kHz, of the reproduction signal A₁ while maintaining the components in the lower-end frequency band B₁, for example, equal to or less than approximately 16 kHz, which is within an audible range, and which corresponds to the guidance voice. The frequency band B₁ is a frequency band in which the emission of a sound by the sound emission device 130 and the reception of a sound by the audio processing device 200 are possible, and this frequency band is included in the frequency band range of sounds of voices or music that the user is exposed to in an ordinary environment (for example, equal to or less than approximately 16 kHz, which is within an audible range). A frequency band b of a modulation signal A_(D) including the identification information D is included in a pass band (frequency band B₁) of the filter 108. As will be understood from the above explanation, the frequency band B₁ of the target signal A_(G) and the modulation signal A_(D) are set to a band that passes the filter 108. The frequency band B₁ is not limited to the above example, and may be a low band equal to or less than 4 kHz or 6 kHz.

A section (a) in FIG. 5 is a diagram illustrative of the relationship between the length of time over which a sound of the reproduction signal A₂ is emitted and the length of time of a sound indicated by the modulation signal A_(D) (hereinafter “notification sound”) and a sound of the target signal A_(G) (guidance voice) that are contained in the reproduction signal A₂. The sound of the reproduction signal A₂ is emitted over a time length Tl. As the section (a) shows, the modulation signal A_(D) that includes identification information D extends over a time length T_(D) from the start of the reproduction signal A₂, and is contained in the time length Tl over which the sound of the reproduction signal A₂ is emitted. The guidance voice that the target signal A_(G) indicates is emitted over a time length T_(G) starting immediately after the emission of the modulation signal A_(D) ends. In other words, among the reproduction signal A₂, the duration of emission of the sound indicated by the modulation signal A_(D) (time length T_(D)) and the duration of emission of the sound indicated by the target signal A_(G) (time length T_(G)) do not overlap. The time length T_(D) over which the modulation signal A_(D) is played is set to a sufficiently shorter time, for example, one to two seconds, compared to the time length T_(G) of the guidance voice.

FIG. 6 is a flowchart showing a flow of the overall operation of the reproduction processing device 120 of the present embodiment. For example, when a playback instruction initiated by the driver O_(P) via the operator 110 is accepted as the carriage C approaches a stop (SA1), the controller 102 reads from the storage device 106 the target signal A_(G) of a guidance voice corresponding to the location in turn corresponding to the playback instruction, as well as the identification information D, and supplies the target signal A_(G) and the identification information D to the signal synthesizer 104 (SA₂). The signal synthesizer 104 generates the reproduction signal A₁ by synthesizing the target signal A_(G) of the guidance voice, which is an audio component of the guidance voice, supplied from the controller 102, and the modulation signal A_(D) that includes the identification information D, which is an audio component that includes the identification information D of the guidance voice, supplied from the controller 102 (SA3). The filter 108 generates the reproduction signal A₂ by extracting the frequency band B₁ from the reproduction signal A₁ generated by the signal synthesizer 104 (SA4). The sound emission device 130 emits a sound indicated by the reproduction signal A₂ that has undergone processing carried out by the filter 108 (SA5).

Audio Processing Device 200

FIG. 7 is a block diagram showing a configuration of the audio processing device 200. The audio processing device 200 of the first embodiment is an audio device that is installed close to the sound emission device 130 of the reproduction system 100, for example, on a surface of a speaker net, and furthermore as shown in FIG. 7, the audio processing device 200 includes a sound receiving device 202, an information extractor 206, a storage device 208, a signal processor 210, and a sound emission device 214. The sound receiving device 202 generates a first audio signal S₁ by receiving a sound of the reproduction signal A₂ emitted from the sound emission device 130 of the reproduction system 100. The first audio signal S₁ contains, in the frequency band B₁, an audio component of the modulation signal A_(D) that includes identification information D (notification sound) and an audio component of the guidance voice. In the first embodiment, the reproduction signal A₂ is less likely to be influenced by noise since the audio processing device 200 is provided close to the sound emission device 130. In other words, the audio processing device 200 is provided at a position that minimizes noise when the sound receiving device 202 receives a sound of the reproduction signal A₂.

The information extractor 206 and the signal processor 210 of FIG. 7 are realized by a computer processing unit (Central Processing Unit: CPU) carrying out a program stored in the storage device 208. The information extractor 206 extracts the identification information D by demodulating the first audio signal S₁ generated by the sound receiving device 202. More specifically, the information extractor 206 extracts the identification information D by selecting, by way of, for example, a band pass filter, a band component of a frequency band b that includes the identification information D within the first audio signal S₁ and allowing the selected band component to pass a matched filter that has, as a coefficient, a spread code used in the spread modulation of the identification information D. In the first embodiment, since the audio processing device 200 is provided close to the sound emission device 130, it is possible to extract the identification information D with high accuracy even when the time length T_(D) of the notification sound is set to a substantially shorter time compared to the time length T_(G) of the guidance voice. The identification information D extracted by the information extractor 206 is stored in the storage device (memory) 208. As will be understood from the above explanation, the identification information D is notified by the reproduction system 100 to the audio processing device 200 in the form of audio communication that uses, as a transmission medium, a sound, namely a sound wave propagated through air in the form of vibrations. The information extractor 206 and all or part of the function of the signal processor may also be realized by use of specific electric circuitry.

The signal processor (second audio signal generator) 210 generates a second audio signal (modulation signal) S₂, which includes the identification information D as an audio component of the higher-end frequency band B₂, by reading from the storage device 208 the identification information D extracted by the information extractor 206, and sequentially carrying out spread modulation of the identification information D using the spread code and frequency conversion using a carrier wave in a particular frequency. The sound emission device 214 emits a sound indicated by the second audio signal S₂ generated by the signal processor 210. In FIG. 7, for convenience of explanation, an A/D converter that converts the reproduction signal A₂ from analog to digital format and a D/A converter that converts the second audio signal S₂ from digital to analog format are not shown.

As shown in FIG. 4, the frequency band B₂ of the second audio signal S₂ differs from the frequency band B₁ of the first audio signal S₁. In other words, the frequency band B₂ of the second audio signal S₂ is higher than the frequency band B₁ of the first audio signal S₁. More specifically, the frequency band B₂ is a frequency in which emission of a sound by the sound emission device 214 and reception of a sound by the terminal device 300 are possible, and this frequency band is included within a frequency band of, for example, between 18 kHz and 20 kHz, which is higher than a frequency band of vocal or musical sounds to which a user is exposed in an ordinary environment, such as a frequency band that is equal to or less than approximately 16 kHz, which is in an audible range. Consequently, the reproduced sound of the second audio signal S₂ that includes the identification information D is barely perceivable to the user of the terminal device 300. In other words, it is possible to transmit the identification information D to the terminal device 300 by audio communication without disruption to the user's hearing of the guidance voice. As will be understood from the above explanation, since, in the first embodiment, there is generated the second audio signal S₂ that includes the identification information D as an audio component of the frequency band B₂, and which differs from the frequency band B₁ of the reproduction signal A₂, even in a case that the reproduction system 100 (filter 108) is configured to suppress the frequency band B₂ so as to emphasize the frequency band B₁ of the guidance voice, it is still possible to notify different terminal devices 300 of the identification information D by audio communication by using the frequency band B₂. In other words, it is possible for the audio processing device 200 to appropriately transmit the identification information D via audio communication without any need to change the reproduction system 100, which is a conventional system that emits a sound indicated by the reproduction signal A₂ in which the frequency band B₂ is suppressed.

Section (b) of FIG. 5 is a diagram illustrative of the second audio signal S₂. As exemplified in section (b), the signal processor 210 of the first embodiment generates the second audio signal S₂ to which the identification information D is added in a repetitive manner in differing sections along the time axis. The sound that the second audio signal S₂ represents is emitted continuously over a time length T₂ from the time the information extractor 206 extracts the identification information D from the sound emitted from the sound emission device 130. In other words, the identification information D is notified to each terminal device 300 via audio communication in a repetitive manner over the time length T₂.

As will be understood from the comparison between section (a) and section (b) of FIG. 5, the time length T₂ over which the sound emission device 214 of the audio processing device 200 emits a sound indicated by the second audio signal S₂ is longer than the time length T_(D) over which the sound emission device 130 of the reproduction system 100 emits the notification sound of the modulated signal A_(D). If the notification sound within the audible range that includes the identification information D is emitted over a protracted period of time, there is a possibility that the user will perceive incongruity or discomfort. In the first embodiment, however, since the length of time over which the notification sound of the frequency band B₁ is emitted is limited to the time length T_(D), it is possible to minimize any possibility that the user will perceive incongruity or discomfort as a result of the notification sound being emitted over a protracted period of time. In contrast, since the signal processor 210 of the audio processing device 200 transmits the identification information D via audio communication by use of a sound in the frequency band B₂, which is barely perceivable by the user, it is possible to notify each terminal device 300 of the identification information D without the user perceiving incongruity or discomfort. Furthermore, since the audio processing device 200 transmits (emits) the identification information D in a repetitive manner over the time length T₂, which exceeds the time length T_(D), even if it is not possible to extract some of the identification information D of the second audio signal S₂, for example, due to interference of mixed noise components, the terminal device 300 can re-acquire the identification information D of other sections.

The time length T₂ of the second audio signal S₂ may be freely set in relation to the time length T_(G) over which a sound (guidance voice) of the target signal A_(G) is emitted. Any of the following configurations may be employed: a configuration in which the time length T₂ of the second audio signal S₂ is longer than the time length T_(G) of the target signal A_(G) (T₂>T_(G)); a configuration in which the time length T₂ of the second audio signal S₂ is shorter than the time length T_(G) of the target signal A_(G) (T₂<T_(G)); and a configuration in which the time length T₂ of the second audio signal S₂ is equal to the time length T_(G) of the target signal A_(G) (T₂=T_(G)). Since the sound of the second audio signal S₂ does not influence the user's hearing the guidance voice, as shown in FIG. 5, a possible configuration may be one in which the period (time length T₂) over which the sound of the second audio signal S₂ is emitted and the period (time length T_(G)) over which the sound (guidance voice) of the target signal A_(G) is emitted overlap each other. In other words, it is possible to configure the two periods to at least partially overlap each other. In such a configuration, since, in parallel to the emission of the guidance voice, an audio signal that includes the identification information corresponding to the guidance voice is emitted, the terminal device 300 can acquire guidance information that corresponds to the notified identification information D more in real-time as compared to, for example, a configuration in which the identification information D is notified after the playback of the guidance voice ends. This is of a great advantage, especially in public transportation services, such as public buses, for which the target locations for guidance are continually changing. There is also an advantage in that the user can more readily recognize the relationship between his/her current location and the guidance information.

FIG. 8 is a flowchart showing the flow of the overall operation of the audio processing device 200. The processing of FIG. 8 is initiated, triggered by the sound emission device 130 emitting a reproduced sound of the reproduction signal A₂ that contains the modulation signal A_(D) including the identification information D and the target signal A_(G). The sound receiving device 202 generates the first audio signal S₁ by receiving the reproduced sound emitted from the sound emission device 130 (SB1). The information extractor 206 extracts the identification information D from the first audio signal S₁ (SB2). The signal processor 210 generates the second audio signal S₂ that is a signal including the identification information D and that is in the frequency band B₂ which is higher than the frequency band B₁ (SB3). The sound emission device 214 emits a sound (sound wave) indicated by the second audio signal S₂ (SB4).

Terminal Device 300

FIG. 9 is a block diagram showing a configuration of the terminal device 300. As shown in FIG. 9, the terminal device 300 includes a sound receiving device 302, an identifier 304, an acquirer 306, and a presenter 308. The sound receiving device 302 is an audio device (microphone) that receives surrounding sounds, and it receives a sound emitted from the sound emission device 214 of the audio processing device 200 and generates an audio signal (hereinafter, the “received sound”) X that indicates a time waveform of the sound. The received signal X includes audio components of the identification information D. For convenience of explanation, an A/D converter that converts the received signal X generated by the sound receiving device 302 from analog to digital format is omitted from the figure.

The identifier 304 extracts the identification information D of the guidance voice by demodulating the received signal X generated by the sound receiving device 302. More specifically, the identifier 304 extracts the identification information D by emphasizing within the received signal X the band component of the frequency band B₂ including the identification information D, for example, by use of a high pass filter, and letting the band component pass a matched filter that uses, as a coefficient, the spread code used in spread modulation of the identification information D.

The acquirer 306 is a communication device that communicates with the guidance information server 500 via the communication network 400 (refer to FIG. 1). The communication scheme for deployment between the terminal device 300 and the guidance information server 500 may be freely selected, but typically, radio communication, for example, information communication that uses radio waves and infrared rays as a transmission medium, is employed that differs from the audio communication used for the audio processing device 200 to notify the terminal device 300 of the identification information D. The acquirer 306 transmits to the guidance information server 500 an information request R that includes the identification information D extracted from the received signal X by the identifier 304. The acquirer 306 receives the guidance information G transmitted from the guidance information server 500 responsive to the information request R.

The guidance information server 500 possesses a guidance information table TB₁ shown in FIG. 10. The guidance information table

TB₁ correlates identification information D (D₁, D₂ . . . ) with guidance information G (G₁, G₂ . . . ). The guidance information server 500, when it receives the information request R including the identification information D from the terminal device 300, reads guidance information G in the guidance information table TB₁ that corresponds to the identification information D in the information request R, and transmits to the terminal device 300, which is the transmitter of the information request R, the guidance information G. The presenter 308 of FIG. 9 presents to the user the guidance information G acquired by the acquirer 306, for example, by causing the guidance information G to be displayed on a display device.

FIG. 11 is a diagram explaining an example display of the guidance information G by the presenter 308. In FIG. 11, an example is shown in which the guidance information G is presented on the presenter 308 of the terminal device 300 as characters indicating the spoken content of the guidance voice. As exemplified in FIG. 11, the user can visually recognize the guidance information G (guidance on the next stop in the example shown in the figure) that is presented on the presenter 308. As will be understood from the foregoing explanation, the user can hear the guidance voice emitted from the sound emission device 130 of the reproduction system 100 and also can read, i.e., recognize by sight the guidance information G presented on the presenter 308. According to the above configuration, it is possible to provide the user with the guidance information G in a manner that is both audibly and visually clear. Also, a hearing-impaired person (a person with hearing disability) can recognize the content of the guidance voice.

In the first embodiment, the audio processing device 200 includes the sound receiving device 202 and the sound emission device 214. While it receives, using the sound receiving device 202, the reproduction signal A₂ emitted from the sound emission device 130 of the reproduction system 100, it emits, using the sound emission device 214, the second audio signal S₂ including the identification information D extracted from the first audio signal S₁. According to the above configuration, it is possible to notify a terminal device 300 of the identification information D via audio communication that uses the frequency band B₂ by disposing the audio processing device 200 close to the reproduction processing device 120, without changing the reproduction system 100 to include a module (signal processor 210) that converts an audio component including the identification information D within the reproduction signal A₂ from the frequency band B₁ to the frequency band B₂.

In the above explanation, an example is given in which the filter 108 of the reproduction system 100 suppresses the frequency band B₂ in the higher range. The cause of the frequency band B₂ being suppressed in a sound emitted from the sound emission device 130 is not limited to this processing by the filter 108. For example, even in a configuration in which there is no filter 108, it is still possible to suppress in the frequency band B₂ the sound emitted from the sound emission device 130 if, for example, the sound emission device 130 is acoustically characterized in that it has difficulty emitting a sound in a high frequency sound range that includes the frequency band B₂. Moreover, it is also possible to use a sound emission device that is capable of emitting the frequency band B₂, although realistically, not all existing devices on carriages C of a public bus service, and the like can be readily upgraded. It is also possible for the frequency band B₂ to be suppressed if a sampling frequency of the target signal A_(G) is too low to include the frequency band B₂ as a target for reproduction. Regardless of how the frequency band B₂ is suppressed, employing the audio processing device of the first embodiment will still enable the transmission of the identification information D via audio communication by using the frequency band B₂.

The sound represented by the second audio signal S₂ is played over the time length T₂ that is longer than the time length T_(D) over which the sound of the modulated signal A_(D) is emitted. If the notification sound that includes the identification information D is overly long as compared to, for example, the guidance voice, there is a possibility that the user will perceive auditory incongruity or discomfort. In the first embodiment, the time length T_(D) over which the notification sound including the identification information D is emitted is configured to be shorter than the time length T₂ of the second audio signal S₂, and thus, it is possible to reduce the number of cases in which the user will perceive auditory unnaturalness or discomfort.

Second Embodiment

Description of a second embodiment of the present invention will be given in the following. With respect to elements in the below exemplified embodiment effects and functions of which are the same as those of the first embodiment are denoted by same reference signs as used in explaining the first embodiment, and detailed explanation thereof is omitted as appropriate.

FIG. 12 is a block diagram indicating a configuration of a reproduction system 100 of the second embodiment. In the first embodiment, an example is given in which the audio processing device 200 is arranged close to the sound emission device 130 of the reproduction system 100. As exemplified in FIG. 12, in the second embodiment, the audio processing device 200 is arranged on a signal line between the reproduction processing device 120 and the sound emission device 130 within the reproduction system 100. A reproduction signal A₂ is supplied as the first audio signal S₁ via the signal line, from the reproduction processing device 120 that generates the reproduction signal A₂ including the target signal A_(G) (audio component of the guidance voice) and the modulation signal A_(D) (audio component including identification information D of the guidance voice).

As will be understood from FIG. 12, the audio processing device 200 of the second embodiment is configured with the sound receiving device 202 and the sound emission device 214 of the first embodiment omitted. At the same time, the audio processing device 200 of the second embodiment includes a signal synthesizer 212 that generates a reproduction signal A₃ by synthesizing (e.g., by addition) the reproduction signal A₂ emitted from the reproduction processing device 120 and the second audio signal S₂. According to the second embodiment, the first audio signal S₁ that has the frequency band B₂ suppressed by the filter 108 of the reproduction processing device 120 is supplied to the information extractor 206 of the audio processing device 200. The information extractor 206 of the audio processing device 200 extracts the identification information D from the first audio signal S₁ (corresponding to the reproduction signal A₂ of the first embodiment) in substantially the same way as in the first embodiment. The signal processor 210 generates, in substantially the same way as in the first embodiment, the second audio signal S₂ that includes, as an audio component in the frequency band B₂ in the higher range, the identification information D extracted by the information extractor 206. The second audio signal S₂ in the frequency band B₂ generated by the signal processor 210 is synthesized with the reproduction signal A₂ by the signal synthesizer 212, and is then emitted from the sound emission device 130. In other words, the sound emission device 130 may be understood as a sound emission means for emitting a sound represented by the reproduction signal A₃ obtained by synthesizing the reproduction signal A₂ with the second audio signal S₂. The terminal device 300 obtains the guidance information G by extracting the identification information D from a sound played by the sound emission device 130.

The above configuration has an advantage over the first embodiment in that it enables the configuration of devices to be simplified, since it is not necessary for the audio processing device 200 to include the sound receiving device 202 and the sound emission device 214. Furthermore, whereas in the first embodiment, it is necessary to ensure that the volume of the modulated signal A_(D) is sufficiently high for the notification sound emitted from the reproduction system 100 to be accurately received by the audio processing device 200, in the second embodiment, it is possible to minimize the volume of the modulation signal A_(D) as compared to the first embodiment since the reproduction processing device 120 and the audio processing device 200 are connected by wire. Moreover, unlike the first embodiment in which the notification sound represented by the modulated signal A_(D) has to be an acoustically natural sound because it is actually emitted, in the second embodiment the necessary level of the volume of the modulated signal A_(D) is reduced as described above, and thus the notification sound does not have to be an acoustically natural sound. It is of note that the above configuration can also be configured to include the sound emission device 214 of the audio processing device instead of the sound emission device 130 of the reproduction system 100.

Instead of having the reproduction system 100 and the audio processing device 200 use the sound emission device 130 in common, as FIG. 13 shows, in this embodiment the reproduction system 100 may use the sound emission device 130, the audio processing device 200, and the sound emission device 214. In other words, the reproduction system 100 emits from the sound emission device 130 the reproduction signal A₂ that is emitted from the reproduction processing system 120. In the meantime, the audio processing device 200 extracts, using the information extractor 206, identification information D from the reproduction signal A₂ supplied by wire from the reproduction processing device 120 and outputs, from the sound emission device 214, the second audio signal S₂ generated by the signal processor 210 and that includes the identification information D. According to this configuration, substantially the same effects as the configuration shown in FIG. 12 can be obtained. An advantage is also obtained in that the device configuration is simplified since it is not necessary to carry out processing by the signal synthesizer 212 (synthesizing the second audio signal S₂ and the reproduction signal A₂).

Third Embodiment

The audio processing device 200 of the first embodiment transmits to the terminal device 300 the identification information D via audio communication that uses a sound as a transmission medium. The communication scheme through which the identification information D is notified to the terminal device 300, however, is not limited thereto. The audio processing device 200 of the third embodiment notifies the terminal device 300 of the identification information D by radio communication (e.g., near field communication) by use of electromagnetic waves, such as infrared rays or radio waves.

FIG. 14 is a block diagram showing a configuration of an audio processing device 200 of the third embodiment. In FIG. 14, the sound emission device 214 of the first embodiment is replaced by a transmitter 216. The signal processor (transmission signal generator) 210 generates a transmission signal that includes identification information D extracted by the information extractor 206. The transmitter 216 is a communication device that transmits an electromagnetic wave that indicates the transmission signal generated by the signal processor 210. The identifier 304 of the terminal device 300 extracts the identification information D included in the received signal received from the audio processing device 200 and transmits to the guidance information server 500 the information request R including the identification information D, and then receives by return guidance information G. Substantially same effects as those of the first embodiment can be obtained by the above configuration.

It is also possible to configure the third embodiment in substantially the same manner as shown in FIG. 13 of the second embodiment. In other words, it is possible to employ a configuration in which the audio processing device 200 of the third embodiment does not include the sound receiving device 202 and in which a reproduction signal A₂ from the reproduction processing device 120 is supplied as a first audio signal S₁ to the audio processing device 200 via a signal line. According to this embodiment, it is possible to minimize the magnitude of a volume of the modulated signal A_(D) compared to the above embodiment in which the reproduction signal A₂ (and eventually the first audio signal S₁) is acquired by the sound receiving device 202, since the reproduction processing device 120 and the audio processing device 200 are connected by wire. In addition, according to this embodiment, a required volume level of the modulated signal A_(D) is reduced, and thus the modulated signal A_(D) need not be an acoustically natural sound.

According to the configuration of the third embodiment, the terminal device 300 is required to be provided with a reception device that receives radio waves or infrared rays that are transmitted from the transmitter 216. In contrast, the first embodiment and the second embodiment have an advantage in that, because the identification information D is notified to the terminal device 300 via audio communication, the sound receiving device 302, which is used for voice calls and video recording, can also be used to receive the identification information D, and thus, there is no need for exclusive reception equipment to be adapted for use in the communication scheme of the transmitter 216.

Modifications

The different embodiments exemplified above may be modified in various manners. Specific modifications are described below as examples. Two or more embodiments that are freely selected from the below examples may be combined as appropriate, as long as they do not contradict one another.

(1) With respect to the reproduction system 100 of each of the abovementioned embodiments, an example configuration is described in which the signal synthesizer 104 generates a reproduction signal A₁ using a target signal A_(G) and identification information D that have been stored in the storage device 106 in advance. However, it is also possible to prepare the reproduction signal A₁ in advance.

FIG. 15 is a block diagram showing a configuration of a reproduction system 100 according to one modification. In the reproduction system 100 of FIG. 15, the signal synthesizer 104 exemplified in each of the abovementioned embodiments is omitted, and the reproduction signals A1 (A₁₋₁, A₁₋₂, A₁₋₃, . . . ) each of which indicate a synthesized sound of the target signal A_(G) (guidance information) and the notification sound of the identification information D are stored in the storage device 106 in advance, for different locations of respective bus stops. Each reproduction signal A₁ that is stored in the storage device 106 is generated in advance in substantially the same way as carried out in the processing by the signal synthesizer 104 in each of the abovementioned embodiments. The controller 102 obtains a reproduction signal A₁ from the storage device 106 in response to an instruction from the driver O_(P) and then supplies the reproduction signal A₁ to the filter 108. According to the above configuration, since it is not necessary to install a signal synthesizer 104 in the reproduction system 100, it is possible to simplify the configuration of the reproduction system 100, or to adopt an existing system in which there is no signal synthesizer 104.

(2) In the first embodiment, an example configuration (section (a) of FIG. 5) is described in which the modulation signal A_(D) (notification sound) and a target signal A_(G) (guidance voice) do not overlap along the time axis. However, it is also possible to have the modulated signal A_(D) and the target signal A_(G) overlap along the time axis. For example, a configuration may be selected in which the modulated signal A_(D) is included in the beginning part of the target signal A_(G). It is of note, however, that the emission of the modulated signal A_(D) as a notification sound in the frequency band B₁ may inhibit audibility of the guidance voice corresponding to the target signal A_(G). In view of this, a preferred configuration would be one in which a notification sound that is audible to the user is not used and in which the modulated signal A_(D), an audio component including identification information D, is synthesized with the target signal A_(G) in such a way as to be barely perceptible to a listener. For example, techniques such as audio watermarking or fingerprinting may be employed to synthesize or extract the identification information D corresponding to the target signal A_(G). (3) In each of the abovementioned embodiments, the audio processing device 200 is applied to the voice guidance system 1 of public bus services, but circumstances in which the audio processing device 200 can be applied are not limited to this example. For example, a configuration may be selected in which the audio processing device 200 is applied to onboard audio announcement systems on other public transportation services such as trains, or to reproduction systems in exhibition facilities. For example, a reproduced sound that is obtained by synthesizing identification information D with a target signal A_(G) of a guidance voice that provides commentary about exhibits can be generated in a reproduction system in an exhibition facility and then received by the audio processing device 200. When a user carrying a terminal device 300 approaches a particular piece of work, a second audio signal S₂ in which the identification information D is synthesized is emitted alongside the guidance voice. The terminal device 300 that the user carries with him/her displays (or emits) guidance information G that is provided from the guidance information server 500 in response to an information request R that includes the identification information D, and it then becomes possible to recognize the guidance information. (4) In each of the abovementioned embodiments, provision of characters representative of a guidance voice to the user is exemplified as the guidance information G, but the content of the guidance information G is not limited to this example. For example, any of the following may be provided to the terminal device 300 as guidance information G: characters and/or still or moving images indicative of information on public transportation services and facilities, such as user guides, facility guides, fares, and so forth; travel guides, such as stops, transfer locations, and so forth; and tourist information for local areas close to the guided location, such as tourist facilities, accommodation, area guides such as for historic sites, and so forth; characters that represent guidance voice, for example, characters to which a hearing-impaired person may refer to visually check guidance information; and/or sounds and/or characters that are obtained by translating the guidance information provided through the guidance voice into a foreign language. In a configuration in which tourist information is provided to the user as the guidance information G, it is possible to have a configuration in which coupons and the like that can be used in tourist and accommodation facilities are presented in the presenter 308 alongside the guidance information G. (5) In the embodiments, an example configuration is described in which the acquirer 306 of the terminal device 300 communicates with the guidance information server 500 via the communication network 400 to transmit to the guidance information server 500 an information request R including identification information D so as to receive guidance information G transmitted from the guidance information server 500 in response to the information request R. However, the method by which the guidance information G is obtained by the terminal device 300 is not limited to this example. For example, a guidance information table TB₁ may be stored in a storage device of the terminal device 300, and the acquirer 306 may acquire the guidance information G corresponding to the identification information D from the storage device. (6) In the embodiments, the voice guidance system 1 is shown by way of example as including the following devices each as a separate unit: the reproduction system 100; the audio processing device 200; the terminal device 300; and the guidance information server 500. However, the configuration of the devices contained in the voice guidance system 1 is not limited to this example. For example, a configuration such as the one in the modification (5) in which the terminal device 300 includes the function of the guidance information server 500 or a configuration such as the one in the second embodiment in which the reproduction system 100 and the audio processing device 200 are included in a single device may be selected. (7) In each of the abovementioned embodiments, an example is described in which the guidance voice represent information on bus stops directed to the user of a public bus is played, but the kind of sound that is emitted by the sound emission device 130 of the reproduction system 100 is not limited to a guidance voice. For example, any of the abovementioned embodiments may be selected in a case in which different sounds such as music is played. As will be understood from the above explanation, the reproduction signal A₂ and the first sound audio signal S₁ related to each of the abovementioned embodiments are comprehensively expressed as a signal that indicates a sound to be reproduced (sound for reproduction).

According to the first embodiment, the sound emission device 214 emits a sound represented by the second audio signal S₂, and according to the second embodiment, either the sound emission device 130 or the sound emission device 214 emits a sound represented by a signal that is obtained by synthesizing the reproduction signal A₂ with the second audio signal S₂. Accordingly, the sound emission device 130 and the sound emission device 214 are comprehensively expressed as a sound emission means of the present invention. The sound emission means of the present invention is thus best understood as a means of emitting a sound represented by a signal that includes at least the second audio signal S₂, i.e., a sound represented by the second audio signal S₂.

(8) Programs according to the abovementioned embodiments may be provided in a format stored in a computer-readable recording medium, and installed in a computer. The recording medium is for example a non-transitory recording medium, and a preferable example thereof may be an optical recording medium (optical disc) such as a CD-ROM, but may also include a recording medium of a freely selected format that is publicly known, such as a semiconductor recording medium or a magnetic recording medium. The program of the present invention may be provided, for example, in a format distributed via a communication network and installed in a computer.

100 . . . reproduction system, 102 . . . controller, 104 . . . signal synthesizer, 106 . . . storage device, 108 . . . filter, 110 . . . operator, 130 . . . sound emission device, 1042 . . . modulation processor, 1044 . . . synthesis processor, 200 . . . audio processing device, 202 . . . sound receiving device, 206 . . . information extractor, 208 . . . storage device, 210 . . . signal processor, 212 . . . signal synthesizer, 214 . . . sound emission device, 300 . . . terminal device, 302 . . . sound receiving device, 304 . . . identifier, 308 . . . presenter, 500 . . . guidance information server. 

1. An audio processing device comprising: an information extractor configured to extract identification information from a first audio signal in a first frequency band in which audio signal there are included an audio component of a sound for reproduction and an audio component that includes the identification information of the sound for reproduction; and a second audio signal generator configured to generate a second audio signal that includes the identification information extracted by the information extractor, and is in a second frequency band, which frequency band is higher than the first frequency band, wherein a sound represented by the second audio signal is emitted by a sound emitter.
 2. The audio processing device according to claim 1, further comprising: a sound receiver configured to receive a sound represented by a reproduction signal including the audio component of the sound for reproduction and the audio component including the identification information of the sound for reproduction, for generation of the first audio signal; and a sound emitter configured to emit a sound represented by the second audio signal generated by the second audio signal generator.
 3. The audio processing device according to claim 2, wherein a length of time over which the sound represented by the second audio signal is emitted by the sound emitter is longer than a length of time over which the audio component including the identification information of the sound for reproduction within the reproduction signal is emitted.
 4. The audio processing device according to claim 2, wherein a period in which the sound represented by the second audio signal is emitted by the sound emitter and a period in which the audio component of the sound for reproduction within the reproduction signal is emitted overlap.
 5. The audio processing device according to claim 2, wherein the sound receiver is arranged close to a sound emission device that emits the sound represented by the reproduction signal.
 6. The audio processing device according to claim 1, wherein a reproduction signal is supplied, as the first audio signal, from a reproduction processing device to the information extractor via a signal line, the reproduction processing device that generates the reproduction signal including the audio component of the sound for reproduction and the audio component including the identification information of the sound for reproduction.
 7. An audio processing device comprising: an information extractor configured to extract identification information from a first audio signal that includes an audio component of a sound for reproduction and an audio component including the identification information of the sound for reproduction; a transmission signal generator configured to generate a transmission signal including the identification information extracted by the information extractor; and a transmitter configured to transmit an electromagnetic wave indicative of the transmission signal generated by the transmission signal generator.
 8. The audio processing device according to claim 7, further comprising a sound receiver configured to receive a sound represented by a reproduction signal that includes the audio component of the sound for reproduction and the audio component including the identification information of the sound for reproduction, for generation of the first audio signal.
 9. The audio processing device according to claim 8, wherein the sound receiver is arranged close to a sound emission device that emits a sound represented by the reproduction signal.
 10. The audio processing device according to claim 7, wherein a reproduction signal is supplied, as the first audio signal, from a reproduction processing device to the information extractor via a signal line, the reproduction processing device generating the reproduction signal that includes the audio component of the sound for reproduction and the audio component that includes the identification information of the sound for reproduction.
 11. An information providing method comprising: extracting identification information from a first audio signal in a first frequency band in which audio signal there are included an audio component of a sound for reproduction and an audio component including the identification information of the sound for reproduction; generating a second audio signal that is a signal including the identification information and that is in a second frequency band, which frequency band is higher than the first frequency band; and emitting a sound represented by the second audio signal.
 12. The information providing method according to claim 11, further comprising emitting the audio component of the sound for reproduction after the emission of the audio component including the identification information of the sound for reproduction, wherein a period in which the sound represented by the second audio signal is emitted and a period in which the audio component of the sound for reproduction overlap.
 13. An information providing method, comprising: extracting identification information from a first audio signal that includes an audio component of a sound for reproduction and an audio component including identification information of the sound for reproduction; generating a transmission signal including the identification information; and transmitting an electromagnetic wave indicative of the transmission signal.
 14. A non-transitory computer-readable recording medium having stored therein a program, the program causing a computer to execute: information extraction processing for extracting identification information from a first audio signal in a first frequency band in which audio signal there are included an audio component of a sound for reproduction and an audio component that includes the identification information of the sound for reproduction; and a second audio signal generation processing for generating a second audio signal that includes the identification information extracted in the information extraction processing and that is in a second frequency band, which frequency band is higher than the first frequency band, wherein a sound represented by the second audio signal is emitted by a sound emitter.
 15. A non-transitory computer-readable recording medium having stored therein a program, the program causing a computer to execute: information extraction processing for extracting identification information from a first audio signal that includes an audio component of a sound for reproduction and an audio component that includes the identification information of the sound for reproduction; transmission signal generation processing for generating a transmission signal including the identification information extracted in the information extraction processing; and transmission processing for transmitting an electromagnetic wave indicative of the transmission signal generated in the transmission signal generation processing. 